1. Field of the Invention
The invention relates to meter proving apparatus for use in test flow meters incorporated in a pipe line for indicating fluid flow rates.
2. Description of the Prior Art
U.K. patent specification No. 865,882 discloses an apparatus for calibrating a meter in a pipe line including a calibration pipe which is fluidly connected into a main pipe line and switches adjacent to each end of and projecting into the calibration pipe and operable by a plug located in the pipe which passes along the pipe with fluid flow. Three-way valves are provided for establishing fluid flow from the pipe line along the calibration pipe in either direction. In order to ensure that the flow in the calibration pipe is fully established before the plug reaches the first of the two switches, it is necessary to provide a considerable length of calibration pipe and whilst this may be satisfactory for a land based system where space is not at premium, it is not acceptable for use on off-shore oil extraction platforms where the space available for such equipment is strictly limited. The object of the present invention is therefore to provide a meter proving apparatus in which fluid flow can be established through the calibration pipe prior to a test operation whilst minimising the length of the calibration pipe.